Researchers in the United Arab Emirates have developed a new model that relies on open-circuit voltage or maximum power point voltage to estimate the operating temperature of PV modules without using sensors.
Researchers at the Dubai Electricity and Water Authority (DEWA) R&D Center have developed a new sensorless self-thermometry approach to estimate the operating temperature of PV modules.
The new method, also called the Shift-Factor method, works by analyzing changes in the open-circuit voltage (Voc) or the maximum power point voltage (Vmp).
“By correlating these electrical responses with irradiance and module temperature, this method not only provides a flexible and non-intrusive approach to temperature estimation, but also serves to verify or correct sensor data, effectively complementing and improving the reliability of traditional sensor-based measurements,” the researchers said.
The work was recently published in “Self-thermometry of PV modules: shift factor approach compared to Sandia, Faiman and IEC 60904-5 models,” Through Advances in solar photovoltaics: research and applications.
It was the result of an effort to establish a “self-sustainable, data-driven approach to estimating module temperature, minimizing dependence on external meteorological inputs, while maintaining accuracy in performance evaluation,” according to corresponding author Shahzada Pamir.
“It builds on existing expertise in modeling, diagnostics and field validation and offers a new approach to sensorless monitoring,” Pamir said. pv magazine. The same organization has been researching remote and non-destructive methods for solar energy performance analysis.
Pamir characterizes the model as a “simplified but robust framework” to estimate the temperature of PV modules directly from electrical parameters, using a shift factor that adapts to real-world conditions.
Comparing the four models, the team found that the Shift-Factor model using Voc achieved the lowest overall root mean square error (RMSE) at 1,600 C, outperforming IEC 60904-5, which was 1,639 C, Sandia at 2,510 C, and Faiman at 3,688 C.
Data from the continuous monitoring of the electrical performance of the outdoor test rig at the DEWA R&D Center in Dubai was used to compare the results. The setup consisted of a variety of PV modules equipped with temperature sensors in a stand-alone configuration, with a tilt angle of 25 degrees.
The team said the IEC 60904-5 method offers “slightly better precision” and lower centralized RMSE, but suffers from greater bias. And it is limited because it relies solely on Voc, which is not always available in commercial systems, while the Shift Factor can use Voc or Vmp, a parameter that is “routinely recorded” by PV inverters via Maximum Power Point Tracking (MPPT), the researchers noted.
They further said that the proposed Shift-Factor model is “broadly adaptable” to other silicon and thin-film PV cell technologies, including bifacial configurations. This is because it is “empirically derived and does not depend on module-specific thermal parameters or heat transfer assumptions,” they said.
The DEWA research group is now integrating the model into broader PV digital twins environments for PV systems. “This next phase focuses on predictive diagnostics and optimization at the system level, with the aim of improving long-term reliability and energy yield prediction for large solar installations operating in desert climates,” Pamir said.
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